On a recent excursion to a park to more accurately measure our local snow depth, I noticed depressions in the snow cover around every tree. This is a very typical occurrence each winter. As we know, snow is not a good absorber of visible light as a high percentage of the sunlight that strikes snow is reflected back into space. But snow does absorb almost all of the infrared energy that strikes it.
The bark of the trees absorbs the energy from the sun and emits infrared (long wave) radiation which the snow nearby absorbs. During this process this long wave radiation is converted to energy which in turn melts the snow near the tree trunk. This gradually creates the depressions in the snow that surrounds each tree.
As long as we maintain our fairly deep snow pack (currently around 12 inches with more possible this weekend) this affect will become even more noticeable in the coming weeks.